Liquid ring pumps are well known. U.S. Pat. No. 4,850,808, Schultze, discloses such a liquid ring pump. The pump is conically ported (conical liquid ring pump) and has one or two stages. The pump includes a housing; a rotor assembly within the housing; a shaft extending into the housing on which the rotor assembly is fixedly mounted; and a motor assembly coupled to the shaft. During operation, the housing is partially filled with operating liquid so that when the rotor is rotating, the rotor blades engage the operating or pumping liquid and cause it to form an eccentric ring that diverges and converges in the radial direction relative to the shaft. Where the liquid is diverging from the shaft, the resulting reduced pressure in the spaces between adjacent rotor blades of the rotor assembly (buckets) constitutes a gas intake zone. Where the liquid is converging towards the shaft, the resulting increased pressure in the spaces between adjacent rotor blades (buckets) constitutes a gas compression zone. A cone shaped member is mated within a cone shaped bore of the rotor assembly. The cone shaped member is ported to allow gas that would otherwise be carried over from the compression zone, to bypass the intake zone and re-enter the compression zone.
U.S. Pat. No. 4,251,190, Brown discloses a water ring rotary air compressor. The compressor includes a housing; a rotor assembly disposed within the housing; a motively powered shaft extending into the housing and fixedly coupled to the rotor assembly. The rotor assembly utilizes a pumping liquid and creates an eccentric ring in a manner similar to U.S. Pat. No. 4,850,808. A port plate or head has a circumferential extension extending into a cylindrical bore of the rotor assembly. A port sleeve is disposed and press fit around the cylindrical extension. The sleeve includes a circumferential groove and a plurality of longitudinally extending slots. The sleeve reduces cavitation.